1. Field of the Invention
The present invention relates to a terminal-modified imide oligomer composition. More particularly, the present invention relates to a terminal-modified imide oligomer composition capable of being easily cured within a relatively short time to produce a cured article having a high mechanical strength, elastic modulus and an excellent heat resistance, especially a high mechanical strength and elastic modulus at a high temperature, and thus usable for producing various heat resistant bonding materials, matrix resins of composite industrial materials containing various reinforcing materials and/or fillers and resins for molding, which materials or resins are useful in very wide applications to, for example, aircraft, space-industrial machines or devices, and vehicle-industrial machines and devices.
2. Description of the Related Art
It is known that thermosetting resins comprising as a major component, a terminal-modified imide oligomer having a relatively low molecular weight, have a higher heat resistance than that of conventional thermoplastic resins, and thus are usable as a matrix resin component of shaped articles or fiber-reinforced composite materials.
Recently, several types of addition curing polyimide resins (imide oligomers) prepared by a polymerization of, for example, pyromellitic dianhydride with an aromatic diamine and an unsaturated reactive compound and having unsaturated terminal radials, have been provided as a matrix resin for prepregs. Almost all of the conventional imide oligomer resins are disadvantageous in that the resins must be prepared by using a specific diamine compound, which is expensive and difficult to obtain, the imide oligomer resins exhibit a low solubility in an organic solvents, and thus are difficult to impregnate in a reinforcing fiber material, a specific organic solvent must be used to prepare the imide oligomer resins, or the imide oligomer resins exhibit a too high melting point, and thus can be converted to shaped articles only at a very high shaping temperature, and this high temperature causes the resultant shaped article to be deteriorated.
Further, the conventional imide oligomer resins do not always have satisfactory curing performances, and thus a too long gelation time of the resin is needed, or the imide oligomer resins have unreacted cross-linking terminal radicals, and therefore, when a composite material is prepared by using the imide oligomer resins, the resultant cured material exhibits a mechanical strength and elastic modulus lower than those expected in view of the chemical structures of the resin.
Furthermore, the conventional imide oligomer resins are disadvantageous in that, when reinforced with fibers, the affinity of the conventional imide oligomer resins to the reinforcing fibers is not satisfactory, and thus in a resultant fiber-reinforced resin articles, the reinforcing fibers are peeled from the resin matrix at the interface therebetween.
Japanese Unexamined Patent Publication (JP-A) Nos. 1-139,632, 1-247,430, 2-64,136, and 2-284,923 disclose several attempts to obtain improved terminal-modified imide oligomer resins able to effectively eliminate some of the above-mentioned disadvantages.
Namely, JP-A-1-139,632 discloses a terminal-modified imide oligomer which is a reaction product of (a) a biphenyltetracarboxylic acid compound with (b) an aromatic diamine and (c) an unsaturated monoamine. This terminal-modified imide oligomer exhibits a high solubility in organic solvents and a relatively low melting point and is useful for providing fiber-reinforced prepregs.
JP-A-1-247,430 discloses a terminal-modified imide oligomer produced by reacting (a) a biphenyl-tetracarboxylic acid compound with (b) an aromatic diamine and (c) a monoamine compound having a carbon-carbon triple bond and having a boiling point of 150.degree. C. to 190.degree. C. under the ambient atmospheric pressure, a vaporization heat of 11 to 16 kcal/mol at a temperature of 25.degree. C., and a vapor pressure of 3 mmHg or less at a temperature of 25.degree. C. This terminal-modified imide oligomer has a high solubility in organic solvents and a relatively low melting point, and thus is useful for producing a fiber-reinforced prepreg.
JP-A-2-64,136 discloses organic fibers produced from a biphenytetracarboxylic acid compound and an aromatic diamine. The organic fibers are useful as reinforcing fibers for a thermosetting resin prepregs.
JP-A-2-284,923 discloses a terminal-modified imide polymer composition usable as a bonding material or a matrix resin of composite materials. The composition comprises at least one flexible terminal-modified imide oligomer (A) selected from (1) terminal-modified imide oligomers produced by reacting biphenyltetracarboxylic acid compounds with aromatic diamine compounds (a) in which a plurality of aromatic cyclic groups are connected to each other directly or through a divalent bonding member consisting of one to 3 atoms and a monoamine compound or carboxylic acid compound having an unsaturated group, and (II) a terminal-modified imide oligomers produced by reacting biphenyltetracarboxylic acid compounds with monoamine compounds having an unsaturated group, and at least one rigid terminal-modified imide oligomer B selected from (III) terminal-modified imide oligomers produced by reacting biphenyltetracarboxylic acid compounds with aromatic diamine compound (b) having a mono-cyclic structure or a polycyclic structure, and a monoamine or carboxylic acid compound having an unsaturated group, and (IV) terminal-modified imide oligomers produced by reacting pyromellitic acid compounds with aromatic diamine compound (c) and monoamine or carboxylic acid compound having an unsaturated group. This terminal-modified imide oligomer is useful for producing cured articles having a high heat resistance, mechanical strength, and elastic modulus.
Nevertheless, the prior arts disclosed in the above-mentioned publications are successful in eliminating only some of the above-mentioned advantages, and the cured materials produced from these imide oligomer resins still have an unsatisfactory mechanical performance and elastic modulus.
Therefore, from the view point of practical use, the conventional imide oligomer resins must be further improved, to eliminate all of the above-mentioned disadvantages.
Accordingly, in the technical field of the shaped resin articles and fiber-reinforced composite materials, the provision of imide oligomer resins satisfying all of the requirements for a high shapability (formability), heat resistance at a high temperature, mechanical strength, and elastic modulus is urgently required.